The original Type 2 SE was based on the "Happy Birthday
Singer" (HBS) chip that was pulled from greeting cards.
These particular models that were modifiable are no longer
available. If only for historical purposes, I've hosted an
old writeup of this design here.

You could also build a Type 2 SE based on a 555 chip, but
a 555-based timer circuit draws over 10X the power of the
HBS (3-6uA for the HBS, 30-65uA for the 555).